Two-voltage circuit-breaker.



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F. E. CASE.

TWO-VOLTAGE CIRCUIT BREAKER.

APPLICATION FILED SEPT. 16. 1914.

1,227,386. Patented May 22, 1917.

Witnesses Inventor:

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FRANK E. QASE, 0F SCHENECTADY, NEW] YQRK, ASSIG'NOR TO GENERAL ELECTRIC COMPANY, A GQFRPQRATIUN 91 NEW) YORK.

TVIO-VQLTi LGE CIRCUIT-BREAKER.

Specification of Letters Patent.

' Patented May 22, Milli.

Application filed September 16, 1914. Serial 3T0; 861,955).

T 0 all whom itmay concern.

Be it known that I, FRANK E. CASE, a citizen of the United States, residing at Schenectady, county of Schenectady, and State of New York, have invented certain new and useful Improvements in El wo- Voltage CircuitBreakers, of which the fol lowing is a specification.

This invention relates to devices for automatically opening an electric circuit in case an abnormally large current is imposed upon it. The invention is especially designed to protect a circuit which operates some times at a low voltage and at other times at a higher one. lnterurban electric railways are now in use which run on 600 volts in the cities and on 1200 volts in the open country. hen operating at the latter voltage, it is customary to connect two motors in series for rull speed, in order to maintain the same voltage drop across each motor as when they operate in parallel on the lower voltage. This arrangement causes the current to be out down to one-half the value it has when operating at 600 volts. It is, therefore, evident that a circuit breaker set to trip for a given overload when the motors are operating with the lower current will trip too soon when they are operating with the higher current.

The object of my invention is to provide a. circuit breaker which will automatically accommodate itself to the changes in voltage and current, and will maintain the same ratio of overload to maximum operating current whichever voltage is in use. I accomplish this by providing the customary circuit -breaker with electromagnetic means connected to the circuit for changing the tripping point of said circuit breaker; preferablyby putting an additional tension on its calibrating spring when the shift is made to the 600 volt section of the line.

The accompanying drawing is a diagrammatic illustration of one mode of can rying out my invention.

From the trolley 1 current flows through a conductor 2 to the motors 3, l, the circuit changes being effected by the usual concuit always with current at 800 volts, a:

dynamotor 8 is provided, and a switch hava current at 600 volts,

ing segments 9 which interpose said dyna motor between the trolley line and the control circuit when the trolley voltage is 1200; the dyuamotor being wound to give This is the condition of operation shown in the drawing. When the switch is thrown to bring the segments 10 into service, the trolley line is connected directly to the control circuit. This will be the situation when the line voltage is 600.

A circuit breaker is interposed in the conductor 2 between the trolley line and the motors. This comprises the usual sta tionary contact 11, movable contact lever 12, toggle 13, catch lever 14. calibrating spring- 15, and series overload coil 10. A. tripping coil 17 acts to withdraw the latch when current is sent through it 'from the control circuit 7 by means of a switch 18. The same switch controls a resetting coil 10 whose movable core is attached to the contact lever 1-2.

The spring 15 is adjusted to exert a certain retarding effect upon the catch lever 14 to give a certain tripping value to the circuit breaker when the normal line voltage is 1200. in order that the circuit breaker may function properly when the car runs upon the 600 volt section of the line, with the consequent doubling of current due to the rearrangement of the motor circuits, 1 provide means for exerting an additional retarding etlect upon the catch lever 14 to raise the tripping point to the proper value. This consists preferably of an auxiliary calibrating spring 20 attached at one end to the lever 14 and at the other to the pivoted armature 21 of an electromagnet 22 whose winding becomes con nected to the control circuit 7 by a contact 23 connected to the segments 10 when the switch is thrown over to connect the troil v line directly with the co rltrol circuit. the clectromagnet 22 is then in shunt to the tripping coil 16 of the circuit breaker. The energizing of this electromagnet draws down its armature 21 and causes the spring 20 to add its tension to that of the main calibrating spring- 15. It will, therefore, require a greater number of ampere turns in the series coil to lift the catch lever and trip the circuit breaker. By properly adjusting the tension the auxiliary sprn 20, the breaker will not trip untii a pr determined overload has been reached with the doubled current due to the 600 volt condition of operation. When the country section of the line is reached, with its 1200 volt current, the motorman will throw the switch 9 back to the position it occupies in the drawing, and in so doing he will automatically release the tension on the auxiliary spring and render it inoperative.

By the simple addition, therefore, of the auxiliary calibrating spring and the electromagnet for putting it into service, I can make the circuit breaker less sensitive when the current increases, and thereby preserve the proper ratio between maximum operation and overload.

In accordance with the provisions of the patent statutes, I have described the prin ciple of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative and that the invention can. be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is 1. The combination with a circuit breaker for a main electric circuit operating on high and low voltage, of suitable translating devices, a control circuit therefor, and a switch controlling the voltage impressed on said control. circuit and simultaneously varying the tripping point of the circuit breaker.

2. The combination with a circuit breaker for a main electric circuit operating on high and low voltage of suitable translating devices, control circuit therefor, electromag netic means for varying the tripping point of the circuit breaker and a. switch for controlling the translating devices and the electromagnetic means.

3. The combination with a circuit breaker for a main electric circuit operating on high and low voltages, of suitable trans ating devices, a control circuit therefor adapted for low voltages, a'sw'itch controlling the voltage impressed on said control circuit, an auxiliary electromagnet controlled by said switch and acting to increase the amount of current required for operating the tripping magnet when the main circuit voltage is low.

4. The combination with a circuit breaker for an electric railway car operating on high and low voltages, of a control circuit for connecting the motors in series for high voltage and in parallel for low voltage, a switch insuring a constant supply of low voltage current for said control circuit, and an auxiliary electromagnet controlled by said switch and acting to increase the amount of current required for operating the tripping magnet of the circuit breaker when the main circuit voltage is low.

5. The combination with a circuit breaker for amain electric circuit operatin on high and low voltages, of suitable trans ating devices, a control circuit therefor adapted for low voltage, a switch controlling the voltage impressed on said control circuit, an auxiliary calibrating spring for the circuit breaker, and an electromagnet controlled by said switch and acting to put tension on 1said spring when the main circuit voltage is 6. The combination with a circuit breaker for an electric railway car operating on high andlow voltages, of a control circuit for connecting the motors in series for high voltage and in parallel for low voltage, a switch insuring a constant supply of low voltage current for said control circuit, an auxiliary calibrating spring for said circuit breaker, an electromagnet for putting tension on said spring, and a contact in said switch-for sending current to said electromagnet when the line voltage is low.

In witness whereof, I have hereunto set my hand this 15th day of September, 1914.

FRANK E. CASE.

Witnesses:

BENJAMIN B. HULL, BENJ. H. VVmsBaon. 

